Protein tyrosine kinase 7 (PTK7), also known as colon carcinoma kinase 4 (CCK4), is a member of the receptor tyrosine kinase superfamily. PTK7 is a type I transmembrane receptor with a large extracellular domain (ECD) containing 7 Ig-like C2 type loops, a transmembrane domain, and a cytoplasmic tyrosine kinase homology domain. PTK7 has been shown to be an important regulator of the Wnt signaling pathways, both canonical and non-canonical, and is linked to the regulation of the planar cell polarity pathway. Functions in cell adhesion, cell migration, cell polarity, proliferation, actin cytoskeleton reorganization and apoptosis. Has a role in embryogenesis, epithelial tissue organization and angiogenesis.